Unable to erase files on ReadyNAS 314

Iam running a readynas 31400, with four 3 Tb western digital drives.  Firmware version 6.9.0.  Recently, while I was logged in as administrator, I tried to use "drag & drop" to transfer a folder from my desktop (Windows 10) to the readynas.  The folder appeared, but upon inspection, I found seven copies of each file within the folder.  I tried to delete the "extra" six files but was unable to from within the admin page.  Feeling a bit frustrated, I tried to delete the whole folder...., with the same "result?".  Finally, I had to go to Windows, create a shortcut to the nas, and access it that way.  Windows access allowed me to delete the files and folder on the nas.  Then I attempted to run diagnostics from the raidar access window.  When I pressed the diagnostics button, it IMMEDIATELY told me the nas was functioning fine.  REALLY????  That must have been a thorough test!  In conclusion, I haven't attempted a "drag & drop" in a while, so I can't say firmware version 6.9.0 is to blame..., but something must be.  A while ago it worked fine.  Good luck with fixing that!